Network protection is quite an essential requirement in transport networks. As it can't be assumed that the end to end link is always available, some form of traffic protection is required via backup link to provide end to end connectivity. In general in any protection mechanism there are M protect entities which protect N work entities.
The three basic components which are used in any of the protection mechanisms are signaling protocol, protection controller and a switch matrix or fabric. The signaling protocol is to co-ordinate between transmit and receive ends (i.e. K-bytes). The protection controller takes the decisions with respect to switching of the traffic. The final component is the switch matrix which selects between the work or protect based on the commands received from the protection controller. The protection controller commands the switch matrix to route the traffic from work or protect. A single protection mechanism is which protects at least one layer. Coexistence of protection mechanisms at multiple layers at the same time is called nested protection. The nested protection is used for enhanced network survivability where protection is configured for at multiple layers and each protection mechanisms healing against the failure at their respective layers.
Each client entity layer and server entity layer of the nested protection mechanism have their own switch fabrics and the decision of switching is taken care at their level itself by a client layer protection controller and a server layer protection controller respectively. A system with distributed switch fabric is costly but nested protection is quite simple to implement there due to the independent protection switching mechanism operating at the respective layers. A system with centralized fabric is quite cheaper to build but for all the switching processes, both the client layer protection controller and the server layer protection layer has to refer to the centralized fabric, due to same complexity of the protection switching mechanism increases
Therefore there is a need for a method of protection switching in a centralized switch fabric of a network element to overcome the above limitations and restrictions.